Morphology of Peroxisomes in Light- and Electron Microscopy

Abstract

Peroxisomes (POs) vary markedly in distribution, morphological shape and enzyme composition in different organs and cell types (for a review see [14]). In the original studies of DE DUVE and associates (for a review see [9]), POs were considered to be present only in a few cell types, like hepatocytes and renal tubular epithelial cells. The development of the alkaline 3,3′-diaminobenzidine (DAB) method for the light- and electron microscopical visualization of the peroxidatic activity of catalase (a marker enzyme of POs)[10, 11] led to the discovery of the ubiquity of this cell organelle [18]. Since POs are involved in the metabolism of long-chain fatty acids, they are very numerous and large in organs metabolizing fatty acids like the liver. Hepatic POs are spherical cell organelles with a single limiting membrane surrounding a homogeneous, finely granular matrix. In some mammalian species (like beef, sheep, cat, rodents), hepatic, or even renal, POs may contain crystalline inclusions in their matrix (cores = crystallized urate oxidase [1, 25]; marginal plates = crystallized α-hydroxy acid oxidase B [29, 30].